1. Enzyme Cofactors and Vitamins
PHL – 213
Biochemistry - I
Co-enzymes
Enzyme Cofactors and Vitamins
Dr. Vidya.D
Asst. Professor,
College of Pharmacy,
Prince Sattam Bin Abdul Aziz University,
Kingdom of Saudi Arabia

2. Objectives
Definition
Classification
Features
Functions

3. Enzyme --Cofactors
A simple enzyme is an active enzyme that consists only of protein.
Many enzymes are active only when they combine with cofactors such as metal ions or small molecules.
A coenzyme is a cofactor that is a small organic molecule such as a vitamin.

4. Enzyme Cofactors (continued)

5. Coenzymes can be classified by their source
1) metabolite coenzymes
synthesized by common metabolites
include nucleoside triphosphates
most abundant is ATP, but also include uridine diphosphate glucose (UDP-glucose) and S-adenosylmethionine
ATP can donate all of its three phosphoryl groups in group-transfer reactions
S-adenosylmethionine can donate its methyl group in biosynthetic reactions.
UDP-glucose is a source of glucose for synthesis of glycogen in animals and starch in plants.

6. 2) vitamin-derived coenzymes
Vitamins are required for coenzyme synthesis and must be supplied in the diet
Lack of particular vitamins causes disease
There are two catagories of vitamins:
1) water-soluble - B vitamins and vit. C
required daily in diet
excess excreted in urine
2) lipid-soluble - vitamins A, D, E, K
Intake must be limited
Stored in fat

7. Function of Coenzymes
A coenzyme prepares the active site for catalytic activity.

8. Metal Ions as Cofactors
Many active enzymes require a metal ion. For example, Zn2+, a cofactor for carboxypeptidase, stabilizes the carbonyl oxygen during the hydrolysis of a peptide bond.

9. Some Enzymes and Their Cofactors

10. Salient features of Coenzyme
Coenzymes are heat stable.
They are low-molecular weight substances.
The coenzymes combine loosely with the enzyme molecules and so, the coenzyme can be separated easily by dialysis.
When the reaction is completed, the coenzyme is released from the apo-enzyme, and goes to some other reaction site.

11. Water-Soluble Vitamins
Water-soluble vitamins are
soluble in aqueous solutions
cofactors for many enzymes
not stored in the body

12. Descriptions of Water-Soluble Enzymes

13. Thiamin (Vitamin B1) Thiamin was the first B vitamin identified
is part of the coenzyme thiamin pyrophosphate (TPP)
is used to decarboxylate -keto carboxylic acids
has a recommended daily allowance (RDA) of 1.2 mg; deficiencies include fatigue, poor appetite, weight loss, nerve degeneration, and heart failure

14. Riboflavin (Vitamin B2)
is found in the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN)
is needed for good vision and healthy skin
has an RDA of 1.2–1.8 mg; deficiencies include dermatitis, dry skin, tongue inflammation, and cataracts

15. Niacin (Vitamin B3) Niacin
is part of the coenzyme nicotinamide adenine dinucleotide (NAD+) involved in oxidation–reduction reactions
has an RDA of 14–18 mg
deficiency can result in dermatitis, muscle fatigue, and loss of appetite

16. Pantothenic Acid (Vitamin B5)
is part of coenzyme A needed for energy production
is involved in glucose and cholesterol synthesis
has an RDA of 5 mg
deficiency can result in fatigue, retarded growth, cramps, and anemia

17. Pyridoxine (Vitamin B6)
Pyridoxine and pyridoxal are
two forms of vitamin B6, which are converted to the coenzyme pyridoxal phosphate (PLP)
required in the transamination of amino acids and decarboxylation of carboxylic acids
has an RDA of 1.3–2.0 mg; deficiency may lead to dermatitis, fatigue, and anemia

18. Cobalamin (Vitamin B12) Cobalamin
consists of four pyrrole rings with a Co2+
is a coenzyme for enzymes that transfer methyl groups and produce red blood cells
has an RDA of 2.0–2.6 μg
deficiencies are pernicious anemia, nerve damage, and malformed red blood cells

19. Ascorbic Acid (Vitamin C)
is required in collagen synthesis and healing of wounds
has an RDA of 60–95 mg
deficiencies are scurvy, weakened connective tissue, slow-healing wounds, and anemia

20. Biotin Biotin is a coenzyme for enzymes that transfer carboxyl groups
has an RDA of 30 g
deficiencies include dermatitis, loss of hair, fatigue, and anemia

21. Folic Acid (Folate) Folic acid (folate)
consists of pyrimidine, p-aminobenzoic acid, and glutamate
forms the coenzyme THF used in the transfer of methyl groups and is involved in the synthesis of nucleic acids
has an RDA of 400  g
deficiencies are abnormal red blood cells, anemia, and poor growth

22. Folic Acid (Folate) (continued)

23. Fat-Soluble Vitamins Fat-soluble vitamins are vitamins A, D, E, and K
soluble in lipids but not in aqueous solutions
stored in the body
important in vision, bone formation, antioxidants, and blood clotting

24. Retinol (Vitamin A) Vitamin A
is needed for retinol (vision); synthesis of RNA
has an RDA of 800  g
deficiencies include night blindness, immune system repression, and slowed growth

25. Cholecalciferol (Vitamin D)
Vitamin D (D3)
is synthesized in skin exposed to sunlight
regulates the absorption of phosphorus and calcium during bone growth
has an RDA of 5–10 μg
deficiency includes weakened bones

26. Tocopherol (Vitamin E)
is an antioxidant in cells
may prevent the oxidation of unsaturated fatty acids
is found in whole grains and vegetables
has an RDA of 15 mg
deficiencies are hemolysis and anemia

27. Menaquinon (Vitamin K)
Vitamin K1 in plants has a saturated side chain.
Vitamin K2 in animals has a long unsaturated side chain.
Vitamin K2 is needed for the synthesis of zymogens for blood clotting.
Vitamin K has an RDA of 90–120 μg.
Deficiencies are prolonged bleeding time and bruising

28. Thank you